在多个请求中保留cookie

Question

我正在尝试以编程方式浏览网站，但是，在我最初成功登录后，之后的任何后续请求似乎都会将我退出，即使我将从上一个响应中检索到的cookie传递给下一个请求。

void Main()
{
    var response = GetResponse(
                        @"https://www.somewebsite.co.uk/account/signin",
                        RequestMethod.Post,
                        string.Format("Credentials.Email={0}&Credentials.Password={1}", "test@test.co.uk", "password")
                        );

    var cookiesToPersist = response.Cookies;

    var nextResponse = GetResponse(
                        @"http://www.somewebsite.co.uk/news",
                        RequestMethod.Post,
                        string.Empty,
                        cookiesToPersist
                        );
}

public HttpWebResponse GetResponse(string url, RequestMethod method, string postData, CookieCollection cookies = null)
{
    var request = (HttpWebRequest)WebRequest.Create(url);
    request.CookieContainer = new CookieContainer();
    if(cookies == null)
        request.CookieContainer.Add(new CookieCollection());
    else
        request.CookieContainer.Add(cookies);

    request.Dump();

    request.Method = (method == RequestMethod.Post) ? WebRequestMethods.Http.Post : WebRequestMethods.Http.Get;
    request.UserAgent = "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2";
    request.AllowWriteStreamBuffering = true;
    request.ProtocolVersion = HttpVersion.Version11;
    request.AllowAutoRedirect = true;
    request.ContentType = "application/x-www-form-urlencoded";

    var byteArray = Encoding.ASCII.GetBytes(postData);
    request.ContentLength = byteArray.Length;

    var stream = request.GetRequestStream();
    stream.Write(byteArray, 0, byteArray.Length);
    stream.Close();

    return (HttpWebResponse)request.GetResponse();
}

public enum RequestMethod
{
    Post,
    Get
}

仍然关注http请求/回复，所以如果这是一个荒谬的简单问题，我道歉。任何帮助将不胜感激。